Hi. Thanks for posting at Healthcaremagic I would keep a possibility of Pityriasis versicolor with post inflammatory hypopigmentation. Pityriasis versicolor is a superficial fungal infection caused by Malassezia Furfur. Pityriasis versicolor commonly affects the areas rich in sebaceous glands e.g the chest, shoulders and back. Hot and humid weather conditions favor the growth of the fungus. Clinically it presents as light colored patches with fine, brawny scaling and post-inflammatory hypopigmentation. Tinea versicolor is easily amenable to treatment either with oral and topical antifungals. A single oral dose of an oral antifungal e.g fluconazole 400 mg is curative OR Itraconazole 200 mg once daily for a week, is an alternative. If i were your treating dermatologist, i would have also asked you to apply 2% ketoconazole lotion over the whole affected while showering and leave it on for 5 minutes daily for 5 days. Post Inflammatory Hypopigmentation persists for months giving the impression of recurrence or resistance to therapy. Moreover, repeated recurrences are common and the patches may seem to persist for ever, with new patches appearing while older ones resolve. Post-inflammatory hypopigmentation takes some time to respond. Re-pigmentation can be hastened by daily sun exposure for 5-10 minutes. Those who have repeated recurrences should use a prophylactic 3 days therapy with topical antifungals, every month i.e 2% ketoconazole lotion over the whole affected while showering and leave it on for 5 minutes daily for 5 days. take care regards